how can I get a number from a popup menu and use it in Push Button

I'm a beginner to MatLab GUI and I'm doing a very simple code .. this is the code for popup menu and pushbtn

function popupmenu2_Callback(hObject, eventdata, handles)
% hObject    handle to popupmenu2 (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
val = get(handles.popupmenu2, 'value');
if (val==1);
  S = 260*10^6
elseif (val==2);
  S = 700*10^6
else
  S = 400*10^6
end

sdf

function solvebtn_Callback(hObject, eventdata, handles)
% hObject    handle to solvebtn (see GCBO)
% eventdata  reserved - to be defined in a future version of MATLAB
% handles    structure with handles and user data (see GUIDATA)
F = str2double( get(handles.force,'string'));
L = str2double( get(handles.length,'string'));
s = S
M = F*L/2;
W = sqrt(4*M/s);
H = 1.5*W;
set(handles.wvalue,'string' , W);
set(handles.hvalue,'string' , H);

here is my problem.. I know the way how I call S is completely wrong but I put it to show you that I want s to take the value of S selected in the popup menu

thank you

%

Answer 1

[Jan]

I'm not sure what you are asking for. I assume it is how to provide the value of S to the other callback. Then:

function popupmenu2_Callback(hObject, eventdata, handles)
handles = guidata(hObject);  % Not sure if handles is up to date already
switch get(handles.popupmenu2, 'value')
case 1
  S = 260e6;  % Cheaper than the power operation
case 2
  S = 700e6;
otehrwise
  S = 400e6;
end
handles.S = S;
guidata(hObject, handles);  % Write back updates of "handles" struct

function solvebtn_Callback(hObject, eventdata, handles)
handles = guidata(hObject);  % get current value
F = str2double(get(handles.force,'string'));
L = str2double(get(handles.length,'string'));
s = handles.S;
...

Does this help already?